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Compositions and methods for detecting and identifying salmonella enterica strains / Life Technologies Corporation




Title: Compositions and methods for detecting and identifying salmonella enterica strains.
Abstract: The present specification describes several novel SNPs of Salmonella enterica subsp. enterica. SNP profiles comprising allelic compositions at each SNP position are described which may be used to identify and differentiate different strains and serovars of Salmonella enterica subsp. enterica. The specification also describes several compositions, methods and kits useful for identifying and differentially distinguishing strains and serovars of Salmonella enterica subsp. enterica. ...


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USPTO Applicaton #: #20120270216
Inventors: Craig Cummings, Elena Bolchakova, Manohar Furtado


The Patent Description & Claims data below is from USPTO Patent Application 20120270216, Compositions and methods for detecting and identifying salmonella enterica strains.

CROSS-REFERENCE TO RELATED APPLICATIONS

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The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/477,142, filed Apr. 19, 2011, the entire contents of which are incorporated herein by reference in their entirety.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted in ASCII format via EFS-Web and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Apr. 12, 2012, is named LT00497.txt and is 6,160,501 bytes in size.

FIELD

The present specification relates, in some embodiments, to compositions, methods and kits for detection and identification of Salmonella enterica subsp. enterica strains and serovars (serological variants). In some embodiments, the disclosure describes several novel single nucleotide polymorphisms (SNPs) and compositions derived therefrom (including probes and primers), which may be used in methods of the disclosure to detect and/or identify a Salmonella enterica subsp. enterica strain from a sample and in some embodiments to identify the serotype of a S. enterica subsp. enterica.

BACKGROUND

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S. enterica strains and serovars are common food borne microbes causing diseases in humans and in animals. Some S. enterica strains cause enteric (intestinal) infections, often referred to as salmonellosis. Other Salmonella enterica strains such as Salmonella Typhi and S. Paratyphi cause typhoid fever.

Traditional serotyping, the standard method for characterization of Salmonella enterica serotypes, is laborious and time consuming, and requires the maintenance of large panels of specific antisera, which is feasible for only a small number of large microbiology reference labs.

Traditional serotyping is also unable to differentiate between evolutionarily distinct subgroups that often exist within a single polypyletic serotype.

SUMMARY

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The present specification relates in some embodiments to identification of several novel single nucleotide polymorphisms (SNPs). These SNPs may be used to differentially identify S. enterica subsp. enterica strains and serovars. In some embodiments, one or more SNP's identified herein may be used to differentiate between closely related strains and serovars of Salmonella enterica subsp. enterica.

The present disclosure in some embodiments provides at least 52 SNPs operable to identify Salmonella enterica subsp. enterica strains and serovars. The fifty two novel SNPs identified herein are comprised in nucleic acid sequences comprised in SEQ ID. NOs:1-52 at position 101 in each of these sequences (see Table 2 attached at the end of the specification). The SNPs located at position 101 are shown in Table 2 by a lowercase nucleotide and correspond to a coordinate position (shown in column 1 of Table 2) in the genomic sequence of Salmonella Enteritidis (also referred to as Salmonella enterica subsp. enterica serovar Enteritidis) described in SEQ ID NO: 53 (which is also described in GenBank ID AM933172.1). SEQ ID NOs: 1-52 comprise SNPs of the disclosure at position 101 and are flanked by 100 bp of genomic DNA on either side (3′ and 5′ side) of the SNP (coordinate positions of left and right flanking sequences in reference of the S. Enteritidis genome are shown in columns 2 and 3 of Table 2).

According to some embodiments, SNPs of the disclosure may be correlated to various Salmonella enterica serotypes and strains and an SNP profile database may be created. Some embodiments describe a computer readable medium used to store a SNP profile database of the disclosure. In some embodiments, a master SNP profile database may be created having all known SNP profiles. An SNP profile of a master database will have data, such as but not limited to, the composition of an SNP allele for each SNP position, and the correlation of SNP allelic compositions at different SNP locations with a serovar and/or a strain.

Assays and methods may be designed using a SNP profile database for analysis and identification including differential identification of Salmonella strains and/or serovars. For example, to determine the strain and/or serovar, a nucleic acid isolated from a Salmonella enterica containing sample, the sample nucleic acid may be tested to determine the allelic composition for at least ten SNPs selected from a larger panel of predetermined SNPs for which serovars have been correlated (such as for example, a master SNP profile database, which in one embodiment may comprise a profile database of the 52 panel of SNPs of the disclosure). The allelic composition of each SNP tested from the sample may then be stored in a sample nucleic acid SNP profile. The sample nucleic acid SNP profile may then be compared with the master SNP profile database to determine the correlation of SNPs and SNP allelic compositions to a particular Salmonella enterica strain and/or serovar. Determining the presence of certain alleles and certain allelic compositions identifies the strain or serovar of Salmonella enterica. Comparison of SNP profiles and correlation may be performed using a computer system or may be performed manually.

In other examples, to determine the strain and/or serovar, a nucleic acid isolated from a Salmonella enterica containing sample, the sample nucleic acid may be tested to determine the allelic composition for at least two, at least three, at least four, at least five, at least six, at least seven, at least eight, at least nine and/or at least ten SNPs selected from a larger panel of predetermined SNPs for which serovars have been correlated (such as for example, a master SNP profile database, which in one embodiment may comprise a profile database of the 52 panel of SNPs of the disclosure).

The present disclosure, in some embodiments, also provides compositions derived from the SNPs of the disclosure. Accordingly, in some embodiments, oligonucleotides comprising primers operable for amplifying (and identifying) one or more SNPs from the nucleic acid of a S. enterica strain are described. Exemplary primers comprise isolated nucleic acid sequences comprised in SEQ ID NOs: 54-105 and SEQ ID NOs: 106-157. However, primers of the disclosure are not limited to the sequences and oligonucleotides disclosed in SEQ ID NOs: 54-157, and one of skill in the art, in light of the present teachings will appreciate that additional primers are also disclosed by the present disclosure. For example, in some embodiments, isolated nucleic acid sequences of the disclosure may have at least 90% sequence identity, at least 80% sequence identity, and/or at least 70% sequence identity to nucleic acid sequences comprised in SEQ ID NOs: 54-157. Other primers may be designed that are to flank a SNP of the disclosure and to form an amplification product comprising an SNP.

In some embodiments, probes operable for identifying one or more SNPs from the nucleic acid of a S. enterica strain are provided. Exemplary probes are described in SEQ ID NOs: 158-209 which correspond to probes for one allele of a SNP, and SEQ ID NOs: 210-261, which correspond to example probes that may be used to identify the other allele of a SNP. In the probes described in SEQ ID NOs: 158-261 (see Table 3), the lowercase nucleotide corresponds to the SNP. However, probes of the disclosure are not limited to the sequences and nucleotides disclosed in SEQ ID NOs: 158-261, and one of skill in the art, in light of the present teachings will appreciate that additional probes are also disclosed by the present disclosure. For example, any nucleotide sequence having at least 10 nucleotides, at least 20 nucleotides, at least 30 nucleotides, or at least 40 nucleotides, comprising a SNP may be used as a probe. For example, in non limiting examples, any nucleotide having at least nucleotides 100-102 of sequences described in SEQ ID NOs: 1-52 and at least 10 additional nucleotides on either the 5′ or the 3′ side of these sequences may be used as a probe of the disclosure. In other non-limiting examples, any nucleotide having at least nucleotides 100-102 of sequences described in SEQ ID NOs: 1-52 and at least 5 additional nucleotides on both the 5′ and the 3′ side of these sequences may be used as a probe of the disclosure. In yet other embodiments, probe sequences of the disclosure may have at least 90% sequence identity, at least 80% sequence identity, and/or at least 70% sequence identity to nucleic acid sequences comprised in SEQ ID NOs: 54-157.

The present disclosure, in some embodiments, describes methods for identifying Salmonella enterica strains and serovars based upon determining the allelic composition of one or more SNPs identified herein. In some embodiments, a method may comprise determining the allelic composition of a panel of at least 10 SNPs to identify and/or differentially detect a strain or a serovar of S. enterica. In some embodiments, a method may comprise determining the allelic composition of all the 52 SNPs to identify and/or differentially detect a strain or a serovar of S. enterica. In some embodiments, a method may comprise determining the allelic composition of a panel of at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9 and/or at least 10 SNPs to identify and/or differentially detect a strain or a serovar of S. enterica.

Determining the allelic compositions and/or genotyping and/or SNP detection may comprises one or more technologies such as but not limited to sequencing (also see the next sentence), amplification, hybridization, high throughput screening methods, bead-based liquid microarray platforms, mass spectrometry, nanostring, microfluidics, chemiluminescence, oligonucleotide ligation, enzyme technologies and combinations thereof. Determining the allelic compositions and/or genotyping and/or SNP detection by sequencing may comprises one or more technologies and/or platforms such as but not limited to genomic sequencing, sequencing targeted regions on CE or semiconductor platforms, multiplex sequencing of all SNP containing regions by CE or semiconductor sequencing and/or by combining with sequencing regions such as but not limited to rfb, fliC and fljB regions on the same platform. Molecular assays to detect SNPs may include amplification performed by a variety of methods such as but not limited to TaqMan®, SnapShot® and other high throughput screening methods know in the art in light of this specification.

Some methods for identifying and/or detecting S. enterica strains and/or serovars in a sample may comprise using an isolated nucleotide sequence composition of the disclosure for detection. Exemplary compositions of the disclosure used for detection methods may comprise, but are not limited to, SEQ ID NO: 54-157, and/or SEQ ID NO:158-261, fragments thereof, at least 10 contiguous nucleotide sequences thereof, complements thereof, isolated nucleic acid sequence comprising at least 90% nucleic acid sequence identity to the sequences set forth above and/or labeled derivatives thereof.

In some embodiments, methods of the disclosure may comprise: isolating a nucleic acid from a sample suspected of having a S. enterica strain and/or a sample from which one desires to detect and/or identify a specific S. enterica strain; amplifying one or more SNP comprising nucleic acid sequences (target nucleic acid sequence) from the nucleic acid from the sample to form an amplification product; and determining the allelic composition of the SNP comprised in the amplified product. Amplification may be repeated using a different set of primer pairs, each primer pair operable to hybridize to and amplify a target nucleic acid sequence comprising another SNP and determining the allelic composition of each SNP until the allelic composition of a panel of SNPs is determined. Once sufficient allelic composition is determined a correlation may be made to which serovar or strain of S. enterica the allelic composition may be assigned to. In some embodiments, at least 10 SNPs allelic compositions may be determined. In some embodiments, a panel of at least 10 SNPs selected from the SNPs comprised in SEQ ID NOs: 1-52 may be amplified and detected. In some embodiments, all SNPs comprised SEQ ID NOs: 1-52 may be amplified and detected to identify and/or type a strain of S. enterica. Amplification reactions may be multiplexed to detect a panel of SNPs.

In some embodiments, a pair of primers used for amplification may comprise the nucleic acid sequence of SEQ ID NO: 54-105, and/or SEQ ID NO: 106-157 and/or labeled derivatives thereof. For example, as shown in Table 3, a primer pair shown as reverse and forward primers may be used to amplify the corresponding SNP in the same row. Thus for example, a primer pair may comprise a first primer and a second primer, the first primer having a SEQ ID NO: 54 may be used as a forward primer, the second primer having a nucleic acid of SEQ ID NO: 106 may be used as a reverse primer may be used to amplify a SNP comprised in SEQ ID NO 1. Primers may be labeled and nucleic acid amplification products may be detected and/or identified by a variety of methods known in the art including but not limited to size analysis of an amplified product; sequencing an amplified product; hybridization with a probe; 5′ nuclease digestion; single-stranded conformation polymorphism; allele specific hybridization; primer specific extension; and oligonucleotide ligation assay.

In some embodiments, methods of the disclosure may comprise: isolating a nucleic acid from a sample suspected of having a S. enterica strain and/or a sample from which one desires to detect and/or identify a specific S. enterica strain; hybridizing one or more SNP comprising regions of the nucleic acid from the sample using one or more probes, each probe designed to bind specifically to a region comprising an SNP; and detecting the hybridized probe-nucleic acid complex. Probes used may be labeled to enable detection. Multiplex hybrid detection maybe enable by using differentially labeled probes. Other detection methods may comprise size analysis of the hybridized product; sequencing an amplified product; hybridization with a probe; 5′ nuclease digestion; single-stranded conformation polymorphism; and/or allele specific hybridization.

In some embodiments, probes used for hybridization and/or for detection of amplified products comprising a SNP may comprise the nucleic acid sequence of SEQ ID NO: 158-209, and/or SEQ ID NO: 210-261, and may comprise labeled derivatives thereof. For example, as shown in Table 3, probes 1 labeled with FAM-MGB and/or probes 2 labeled with VIC-MGB may be used to identify the corresponding SNP in the same S. Entritidis coordinate position (see Tables 2 and 3). Thus for example, probes having SEQ ID NO: 158 and SEQ ID NO: 210 may be used to hybridize to an SNP comprised in SEQ ID NO: 1. Each probe is operable to hybridize to one allelic composition of the SNP described in SEQ ID. NO: 1. For example, probe having SEQ ID NO: 158 has a “g” (guanine) at the complementary position, hence it is operable to selectively hybridize to an allelic variant of the SNP in SEQ ID NO: 1 having a “c” (cytosine) allelic composition, whereas probe having SEQ ID NO: 210 has an “a” (adenine) at the complementary position, hence it is operable to selectively hybridize to an allelic variant of the SNP in SEQ ID NO: 1 having a “t” allelic composition. In some embodiments, both probes may be used to determine what the allelic composition of the SNP in SEQ ID NO: 1. For example, a first probe labeled with a first label may be used to hybridize to one allele of the SNP (of SEQ ID NO. 1 for example having the “c” allelic composition) and a second probe labeled with a second label may be used to hybridize to the other allele of a SNP (of SEQ ID NO: 1, this may be for example the “t” allelic composition. In this example embodiment of SEQ ID NO. 1, if a first probe of SEQ ID NO: 158 and a second probe of SEQ ID NO: 210 are used and only the FAM-MGB signal is detected, the allelic composition of the SNP in SEQ ID NO: 1 is “c.” If however, only the VIC-MGB signal is detected, the SNP allelic composition of the SNP of SEQ ID NO: 1 is “t.”

In some embodiments, a panel of at least 5 and/or at least 10 SNPs selected from the SNPs comprised in SEQ ID NOs: 1-52 may be amplified and the composition of the SNP determined. In some embodiments, all SNPs comprised SEQ ID NOs: 1-52 may be amplified and the allelic composition determined to identify and/or type a strain of S. enterica.

Molecular assays to detect SNPs may include amplification performed by a variety of methods such as but not limited to TaqMan®, SnapShot® and other high throughput screening methods know in the art in light of this specification.

Methods of the disclosure may also comprise determining the allelic compositions (i.e. genotyping and/or SNP detection) by one or more technologies in addition to amplification such as but not limited to sequencing, hybridization, hybridization on bead-based liquid microarray platforms, high throughput screening methods, mass spectrometry, nanostring, microfluidics, chemiluminescence, oligonucleotide ligation, enzyme technologies and combinations thereof. In methods of the disclosure, determining the allelic compositions by sequencing may comprises one or more technologies and/or platforms such as but not limited to genomic sequencing, sequencing targeted regions on CE or semiconductor platforms, multiplex sequencing of all SNP containing regions by CE or semiconductor sequencing and/or by combining with sequencing regions such as, but not limited to, rfb, fliC and fljB regions on the same platform.

Methods of the disclosure may provide one or more advantages listed here. For example, in some embodiments, the methods provide a molecular assay in contrast to traditional immunoassays which may be easier, and/or faster, and/or allow for portable testing options, and/or that may be performed in more accessible settings than traditional serotyping methods.

Some embodiments of the present disclosure provide kits for detection and/or differential detection and/or identification of S enetrica strains. A kit of the disclosure may comprise one or more isolated nucleic acid sequences of the disclosure as set forth herein. Some nucleic acid compositions of the disclosure may comprise primers for amplification of target nucleic acid sequences comprising one or more SNPs that are specific to one or more strains of a S. enterica that may be present in a sample. Some nucleic acid compositions of the disclosure may comprise probes for the detection of target nucleic acid sequences and/or amplified target nucleic acid regions comprising one or more SNPs from a S. enterica strain present in a sample. Probes and primers comprised in kits may be labeled. Kits may additionally comprise one or more components such as, but not limited to: buffers, enzymes, nucleotides, salts, reagents to process and prepare samples (e.g., reagents to isolate nucleic acids), probes, primers, agents to enable detection and control nucleotides. Each component of a kit of the disclosure may be packaged individually or together in various combinations in one or more suitable container means.

While specific advantages have been disclosed hereinabove, it will be understood that various embodiments may include all, some, or none of the previously disclosed advantages. Other technical advantages may become readily apparent to those skilled in the art in light of the teachings of the present disclosure.

These and other features of the present teachings will become more apparent from the detailed description in sections below.

BRIEF DESCRIPTION OF THE DRAWINGS

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stats Patent Info
Application #
US 20120270216 A1
Publish Date
10/25/2012
Document #
File Date
12/31/1969
USPTO Class
Other USPTO Classes
International Class
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20121025|20120270216|compositions and methods for detecting and identifying salmonella enterica strains|The present specification describes several novel SNPs of Salmonella enterica subsp. enterica. SNP profiles comprising allelic compositions at each SNP position are described which may be used to identify and differentiate different strains and serovars of Salmonella enterica subsp. enterica. The specification also describes several compositions, methods and kits useful |Life-Technologies-Corporation
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